If your soil contains no or low nutes you should be fine then. But your "peat-based" soil looks like mostly wood chips. The Hydroton should help draining.
I was perhaps misled by the visually poor look of the soil ... i was sure you were using cheap "prefertilized' soil and experiencing nute burn.
However seedlings often have defects like dead tips that have nothing to do with the grow or grower.
I looked up Formulex and cannot find specifics on its ingredients or the NPK analysis. if you're going to grow organic, i recommend researching soil amendments, like giano, castings etc. You can get great nutrient profiles "dirt cheap" if you educate yourself on sourcing organics ... and double especially if you do your own composting. cn